Project Summary/Abstract Anxiety is the most prevalent childhood mental health disorder (Kessler 2012). Because childhood anxiety disorders can be disabling and often persist into adulthood, addressing these conditions early in childhood is an important target for secondary prevention. The recently reported 51% increase in major depressive disorder among teens ages 12-17 from 2005 to 2017 (8.7% to 13.2%) (Twenge 2019) underscores the importance of addressing mental health (MH) problems in this age group. It is not known what impact pets have on sub-threshold or as yet undiagnosed child behavioral and emotional problems, or the development of MH disorders. Because pet dogs may be salient agents for child emotional development, they may ameliorate childhood anxiety or mood disorders through attachment. If so, positive child-dog interactions could prevent the evolution of these problems into full-fledged MH disorders in adolescence or later life. Our prior cross-sectional human animal interaction study funded by NICHD showed that children with pet dogs had lower anxiety scores (for separation and social anxiety) than children without pet dogs. The current study will be a 7.5 year follow-up of these children who now range in age from 11-17 years. Of the original sample, 85% (544) have had at least one visit in our rural health network in the past year, which enables us to contact and follow-up these youth. Using the electronic medical record (EMR), we will determine whether youth with pet dog exposure have a lower prevalence of MH diagnoses 7.5 years later relative to the comparison group without pet dog exposure. We will also analyze parent or youth self-reported symptom measures ascertained at follow-up using validated instruments to detect subthreshold levels of mood disorders or threshold level but as yet unrecognized or diagnosed MH problems that lead to significant impairment. Given the lack of information about the effects of a pet cat on childhood MH and development, the same analysis will be applied to youth with pet cat exposure compared to youth without pets. This R21 application leverages our prior RO-3 results to conduct a naturalistic, longitudinal analysis of the relationship between pet dog or cat exposure and subsequent development of teen MH symptoms and illness. This follow-up study captures the full spectrum of mental illness from subthreshold to unrecognized threshold MH symptoms to MH diagnosis in these teens. Analysis will include adjustment for a large number of potential covariates. The results will enable future research studies to focus on specific MH diagnosis and/or symptomatology as a next step in elucidating underlying mechanisms in HAI, as well as develop evidence based advice that clinicians can relay to parents.